Process for removing sulphur from vulcanized rubber



Patented June 1, 1926.

UNITED STATES PATENT OFFICE.

LELAND L. ODOM, F MEMPHIS, TEE'NESSEE, ASSTGNOR OF ONE-THIRD TO E. M.ELLIS,

0F MEMPHIS, TENNESEE, A ND ONE-THIRD TO J. D. REYNOLDS, OF CAMDEN, AR-

' KANSAS.

' EROOESS FOR REMOVING SULPHUR FROM VULC AN IZED RUBBER.

Ne Drawing.

My invention relates to the treatment of vulcanized rubber, trimmingsand rubber .scrap material, and has for its principal object theprovision of a new and improved I process for the removal of sulphurfrom such material.

Another object of the invention is the provision of such a processwherein rubber in its pro-vulcanized state is recovered.

lVith these, and such other objects in View as will be apparent from thedescription to those skilled in the art, my invention resides in thenovel process and treatment hereinafter described and claimed.

At the present time the removal of sulphur from vulcanized rubber is oneof the greatest unsolved problems confronting the rubber industry. Manyprocesses for accomplishing this result have been tried, and 2 manyattempts have been made, but none have proved practical, and have beencommercially abandoned. The known methods usually embrace an acid. oralkaline treat ment as solvents, efforts having been made 25 to splitofl the sulphur atom in the vulcanized molecule, reducing it back to anunsaturated hydrocarbon condition, to bring the original hydrocarboninto a form capable of the same degree of vulcanization it possessedbefore vulcanization.

The formula for caoutchouc is C H and that of vulcanized rubber C H SDue to the complex condition of rubber and the very strong aifinity forsulphur, it is not Application filed January 7, 1925. Serial minrioi.

vulcanized rubber,-efi'ect a' combination of the sulphur and'solvent andevaporate off to recover unvulcanized rubber.

agents that are powerful enough to remove Many attempts have been made,but any'known rethe combined sulphur, render the rubber unfit forcommercial use.

The essential principle of my process lies in a splitting of thecaoutchouc molecules of the vulcanized rubber with accompanying removalof the'sulphur atoms, and a reuniting of the split molecules to originalform after sulphur removal.

Caoutchouc, C H, when its molecules are split, resolves into 2C H which,is

isoprene. Isoprene when placed over metallic sodium, undergoespolymerization forming caoutchouc. In order to make use of this action,it is necessary at some point to remove the sulphur atom in thetreatment of vulcanized rubber.

I accomplish this result by distilling vulcanizcd rubber in a stillwhich is heated by superheated steam, through metallic wool. In thepassage of the still vapor through the wool, the affinity of sulphur forthe metal is'so strong that it will leave the caoutchouc and combinewith the metal; and

the heat of the still causing a splitting of the caoutchouc molecule,the resulting distillate will be isoprene free of sulphur.

The liquid distillate, isoprene, is then I placed over metallic sodiumand polymerizes, forming oaoutchouo. The formula is as folpossible byknownmethods to dissolve the. lows;

n H H, H a 11, 1|; E B it B, o o I! a o o 01 7-0 O on?! b-om 11-6 -omif, t. g a i. i. i. i. caontchouo-i-heat 20mm eaoutohouo The vulcanizedrubber may either be distilled directly through the metallic wool, orthe distillate may be redistilled through the 'Wool, as is mostpracticable. I have found that copper WOOl gives best results, butsteel,'iron, and many other metals may be employed.

is distilled away.

a An importantresult in my process lies in the recovery of fabricmaterial incorporated in such material as oldtiresand the like treatedfor the recovery of rubber. By using superheated steam, the fabricmaterial is preserved in its original state, asthe rubber All otherknown proc- 1 be made as will fell within the scope of'the essesldestroythe fabrics By use oflecids'or elkalis. l I

I havejfound that best resultsere obtained in polymerization, by usingone part metallic sodium to twenty parts isoprene, and these proportionsareembodied in my process. 4

While I'have described certain steps and details as well as materialsentering into the invention, I desire it to he understood that theinvention is not limited thereto, but that any desired changes andmodifications may invention as claimed.

isoprenei menses 1 claimza 4 g 4 ii. In a rocess forremov ng sulphurfrom vulcemze rubber, the dlstllla'tlon of such rubber through metallicWool to produce A Process for the 'treetment of material containingvulcanized rubber, comprising distilling said material through asubstance having a stronger affinity for sulphur than 'therubber of thematerial, said substance

